Impact of Missing Data for Body Mass Index in an Epidemiologic Study

To assess the potential impact of missing data on body mass index (BMI) on the association between prepregnancy obesity and specific birth defects

Detection of Pelvic Inflammatory Disease: Development of an Automated Case-Finding Algorithm Using Administrative Data

ICD-9 codes are conventionally used to identify pelvic inflammatory disease (PID) from administrative data for surveillance purposes. This approach may include non-PID cases. To refine PID case identification among women with ICD-9 codes suggestive of PID, a case-finding algorithm was developed using additional variables. Potential PID cases were identified among women aged 15–44 years at Group Health (GH) and Kaiser Permanente Colorado (KPCO) and verified by medical record review. A classification and regression tree analysis was used to develop the algorithm at GH; validation occurred at KPCO. The positive predictive value (PPV) for using ICD-9 codes alone to identify clinical PID cases was 79%. The algorithm identified PID appropriate treatment and age 15–25 years as predictors. Algorithm sensitivity (GH = 96.4%; KPCO = 90.3%) and PPV (GH = 86.9%; KPCO = 84.5%) were high, but specificity was poor (GH = 45.9%; KPCO = 37.0%). In GH, the algorithm offered a practical alternative to medical record review to further improve PID case identification

"Toward a Clearer Definition of Confounding" Revisited With Directed Acyclic Graphs

In a 1993 paper (Am J Epidemiol. 1993;137(1):1–8), Weinberg considered whether a variable that is associated with the outcome and is affected by exposure but is not an intermediate variable between exposure and outcome should be considered a confounder in etiologic studies. As an example, she examined the common practice of adjusting for history of spontaneous abortion when estimating the effect of an exposure on the risk of spontaneous abortion. She showed algebraically that such an adjustment could substantially bias the results even though history of spontaneous abortion would meet some definitions of a confounder. Directed acyclic graphs (DAGs) were introduced into epidemiology several years later as a tool with which to identify confounders. The authors now revisit Weinberg's paper using DAGs to represent scenarios that arise from her original assumptions. DAG theory is consistent with Weinberg's finding that adjusting for history of spontaneous abortion introduces bias in her original scenario. In the authors' examples, treating history of spontaneous abortion as a confounder introduces bias if it is a descendant of the exposure and is associated with the outcome conditional on exposure or is a child of a collider on a relevant undirected path. Thoughtful DAG analyses require clear research questions but are easily modified for examining different causal assumptions that may affect confounder assessment

The association between gestational weight gain z-score and stillbirth: a case-control study

Background There is limited information on potentially modifiable risk factors for stillbirth, such as gestational weight gain (GWG). Our purpose was to explore the association between GWG and stillbirth using the GWG z−score. Methods We analyzed 479 stillbirths and 1601 live births from the Stillbirth Collaborative Research Network case−control study. Women with triplets or monochorionic twins were excluded from analysis. We evaluated the association between GWG z−score (modeled as a restricted cubic spline with knots at the 5th, 50th, and 95th percentiles) and stillbirth using multivariable logistic regression with generalized estimating equations, adjusting for pre − pregnancy body mass index (BMI) and other confounders. In addition, we conducted analyses stratified by pre − pregnancy BMI category (normal weight, overweight, obese). Results Mean GWG was 18.95 (SD 17.6) lb. among mothers of stillbirths and 30.89 (SD 13.3) lb. among mothers of live births; mean GWG z−score was − 0.39 (SD 1.5) among mothers of cases and − 0.17 (SD 0.9) among control mothers. In adjusted analyses, the odds of stillbirth were elevated for women with very low GWG z−scores (e.g., adjusted odds ratio (aOR) and 95% Confidence Interval (CI) for z−score − 1.5 SD versus 0 SD: 1.52 (1.30, 1.78); aOR (95% CI) for z−score − 2.5 SD versus 0 SD: 2.36 (1.74, 3.20)). Results differed slightly by pre − pregnancy BMI. The odds of stillbirth were slightly elevated among women with overweight BMI and GWG z−scores ≥1 SD (e.g., aOR (95% CI) for z−score of 1.5 SD versus 0 SD: 1.84 (0.97, 3.50)). Conclusions GWG z−scores below − 1.5 SD are associated with increased odds of stillbirth

Diabetes mellitus, smoking status, and rate of sputum culture conversion in patients with multidrug-resistant tuberculosis: a cohort study from the country of Georgia.

Diabetes mellitus (DM) is a risk factor for active tuberculosis (TB) but little is known about the effect of DM on culture conversion among patients with multidrug-resistant (MDR)-TB. The primary aim was to estimate the association between DM and rate of TB sputum culture conversion. A secondary objective was to estimate the association between DM and the risk of poor treatment outcomes among patients with MDR-TB.A cohort of all adult patients starting MDR-TB treatment in the country of Georgia between 2009-2011 was followed during second-line TB therapy. Cox proportional models were used to estimate the adjusted hazard rate of sputum culture conversion. Log-binomial regression models were used to estimate the cumulative risk of poor TB treatment outcome.Among 1,366 patients with sputum culture conversion information, 966 (70.7%) had culture conversion and the median time to conversion was 68 days (interquartile range 50-120). The rate of conversion was similar among patients with MDR-TB and DM (adjusted hazard ratio [aHR] 0.95, 95%CI 0.71-1.28) compared to patients with MDR-TB only. The rate of culture conversion was significantly less in patients that currently smoked (aHR 0.82, 95%CI 0.71-0.95), had low body mass index (aHR 0.71, 95%CI 0.59-0.84), second-line resistance (aHR 0.56, 95%CI 0.43-0.73), lung cavities (aHR 0.70, 95%CI 0.59-0.83) and with disseminated TB (aHR 0.75, 95%CI 0.62-0.90). The cumulative risk of poor treatment outcome was also similar among TB patients with and without DM (adjusted risk ratio [aRR] 1.03, 95%CI 0.93-1.14).In adjusted analyses, DM did not impact culture conversion rates in a clinically meaningful way but smoking did

Serum Polybrominated Biphenyls (PBBs) and Polychlorinated Biphenyls (PCBs) and Thyroid Function among Michigan Adults Several Decades after the 1973-1974 PBB Contamination of Livestock Feed

In 973-1974, Michigan residents were exposed to polybrominated biphenyls (PBBs) through an accidental contamination of the food supply. Residents were enrolled in a registry assembled after the incident, and they and their children participated in follow-up studies to assess subsequent health outcomes. OBJECTIVES: We evaluated associations between serum PBBs and polychlorinated biphenyls (PCBs) and markers of thyroid function among Michigan adults. METHODS: Serum concentrations of four PBB and four PCB congeners were measured at least once in 753 adults, including 79 women who participated in a 2004-2006 study and 683 women and men with follow-up during 2012-2015. Participants completed questionnaires on health conditions (including physician-diagnosed thyroid disease), behaviors, and demographics. Thyroid hormones were measured in a subset without thyroid disease (n = 551). In multivariable linear regression models, PBB and PCB congener concentrations, on both the volume (nanogram/milliliter) and lipid (nanogram/gram lipid) basis, were assessed in relation to thyroid hormones. Logistic regression models were used to estimate associations between serum PBBs and PCBs and thyroid disease. RESULTS: Thyroid disease was common (18% overall 25% among women). Among women, all odds ratios (ORs) for PBB-153 and thyroid disease were positive for quintiles above the reference level, but estimates were imprecise and were without a monotonic increase. For an interquartile range (IQR) increase in PI313-153 (0.43 ng/mL), the OR (any thyroid disease) = 1.12(95% CI: 0.83, 1.52) (n = 105 cases)for hypothyroidism, OR = 1.35 (95% CI: 0.86, 2.13) = 49 cases). There were 21 cases of thyroid disease in men [OR = 0.69 (95% CI: 0.33)1.44 for an IQR increase (0.75 ng/mL) in serum PBB-1531. PCB congeners were statistically significantly associated with greater total and free thyroxine and total triiodothyronine among women and with total and free triiodothyronine among men in lipid-standardized models. CONCLUSIONS: We found some evidence to support associations of PBBs and PCBs with thyroid disease and thyroid hormone levels